The humpback whale ~Megaptera novaeangliae is well known among the baleen whales in its
ability to perform acrobatic underwater maneuvers to catch prey. In order to do these
and turning maneuvers, humpback whales use extremely mobile flippers. The humpback whale
fin is unique because of the presence of bumps or tubercules on the leading
edge which gives this surface a frilly baroque scalloped appearance.
The addition of leading-edge tubercles to a scale model of an idealized humpback whale flipper
delays the stall angle by approximately 40%, while increasing lift and decreasing drag
Leading-edge tubercles delay stall on humpback whale „Megaptera novaeangliae… flippers
D. S. Miklosovic
http://pof.aip.org/phfle6/v16/i5/pl39_s1?isAuthorized=no
In sum, we find a 4.8% increase in lift, a 10.9% reduction in induced drag, and a
17.6% increase in lift to drag ratio when compared with the wing shown in Fig. 1.
From:
THE INFLUENCE OF PASSIVE, LEADING EDGE
TUBERCLES ON WING PERFORMANCE
P. Watts
Applied Fluids Engineering, Inc.
Private Mail Box #237, 5710 E. 7th Street, Long Beach, CA, 90803
phil.watts@appliedfluids.com
F. E. Fish
West Chester University
Department of Biology, West Chester, PA,
Thankyou arshad :)
ReplyDeleteThe humongous cargo ships and tankers also feature a bulbous nose at the front which helps to ease the water flow around the bulky plan shape of the hull, I think you are definately cookin' on gas with this whale inspired fin.
ReplyDeleteHope it turns out great!
Thanks Malletto ! Those bulbs on the cargo ships work in a specific speed range and require a displacement hull which doesn't change its waterline length, so I'm not sure that we could apply them to surfboards. Possibly on a pure displacement hull olo specialised for riding unbroken waves ?
ReplyDeleteI remember posting a link for this on the Tree to Sea forum more than a year ago. Glad to see someone trying it out. I've been too stoked on riding surf mats to work on surfboards. Curious to see how it works.
ReplyDeleteIt's odd that there's been so much talk about the 'whale bumps' for so long but only a few people have been using them. We discussed them a lot on Swaylocks back in 2003/4 and if I remember correctly one Swaylocks member even patented them for surfboard fin applications. My interest in the was given a major boost by some information sent by a friend in Spain who makes hydrofoil boards. He mentioned that tests had shown that the bumps reduce tip drag, which seems obvious now but I'd been under the impression that they only improved the angle of attack capability, not the lift/drag ratio.
ReplyDeleteWe'll let you know how they feel, glad that you are enjoying the surf mats, by all accounts they are incredible wave craft.
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I tubercled a 9" 4a. The performance was very noticeable. The fin would turn tighter arcs without stalling. It also allowed my board to trim more parallel to the wave face without letting the tail slide out. I've been testing them in my transitional, round bottom boards. I really like the performance of my tubercled fins. I also tubercled a twin fin and it cured stalling that I would experience with a normal twin. Hail mother nature.
ReplyDeleteLV
Great stuff LV, thanks for the report. That's a Greenough fin isn't it ? The ability to handle higher angles of attack should also allow a thinner fin to be used if desired, for even more drag reduction. I've been tuberculing a new fin for the jet 7'8" today, it's nice to do I think.
ReplyDelete